Protractor



o. syREAM'Y. PROTRAGTOR.

(Model.)

Patented Apr. 7, 1891..

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UNITED STATES PATENT OFFICE.

CHRISTOPHER S.A REAMY, OF BOSTON, MASSACHUSETTS.

PROT RACTO R.

SPECIFICATION forming part of Letters Igatent No. 449,782, dated Aprl- '7, 1891.

Application filed December 6, 1890. Serial No. 373,737. (Model.)

To all whom it may concern.-1

Be it known that I, CHRISTOPHER S. REAMY, a citizen of the United States, residing at Boston, in the county of Sudolk and State of Massachusetts, have invented certain new and usefullmprovements in Protractors and Try- Squares; and I do herebydeclare the following to be a full, clear, and exact description ot' the invention, such as will enable others skilled in the art to which it appertains to make and use the same, reference being had lto the accompanying drawings, and to letters of reference marked thereon, which form a part of lthis specification.

This invention relates to protractors and try-squares-in other words, instruments for laying out angles `generally of any number of degrees from zero to one hundred and eighty degrees, and for ascertaining the angle of two surfaces with respect to each other, and for any or all purposes where a similar object is sought to be obtained.

The drawings represent, in Figure l, a plan of an instrument embodying thy-invention. Fig. 3 is an elevation ot' Fig. l. Fig. 2 is a ver- Fig. 4 is a reverse view of Fig. l.

The instrument embodying my invention consists, primarily, of two arms graduated or otherwise and pivotallyvunited in such manner that both arms shall swing in the same plane and about a central point, which shall be the two adjacent corners at one end of each of said arms. Further, one of these arms is furnished with a protractor, the other with a pointer. Hence the angle subtended between said arms is always indicated by said pointer upon the protractor.

In the drawings I have shown a pair of arms A B, graduated with linear units further subdivided after the manner otl a footrule. These arms are, moreover, united so as to move and swing with a circular or radial motion about a central point. This point is at the adjacent corners of one end of each of said arms. Hence the arms maybe swung from zero or no degree--that is, when their edges upon corresponding sides are contiguous through an arc of one hundred and eighty degrees, or made to'assume suchposition that the two ends are contiguous, and the edges of said arms then form a continuous straight line. To permit two corners of said arms to form a central point, as before premised, I secure by brazing or otherwise two posts a b at or near the ends of said arms to be united. The posts are vert-ical or at right angles to the faces of the arms. Further, the post a is provided with a cylindrical offset or hollow sleeve c, the center of which is adjusted accurately above the two adjacent corners of the arms, which point is the center of rotation for the latter. Moreover, the post b is furnished with an offset from which rises a pintle d, of a di" ameter to snugly iit the hollow sleeve o. The joint thus created and by which the two arms are united and given swinging movement is coincident with the central point at the corner of one end of each ofsaid arms. In order to measure the angle subtended by said arms, I have surmounted and affixed to the post a, by means of a screw e, a protractor C, the center of which is the center ot the pintle or joint for the arms A B, while upon the pintle d is securely mounted a pointer f, which likewise pivots on the pintle as a center. Hence it will be understood that the center or point of rotation for the arms and for the pointer coincides with the central longitudinal axis of the joint, as likewise the center of the protractor. Therefore in measuring an angle subtended by two lines the adjacent corners of the arms are centered at the apex ot the angle and the inside edges of the arms caused to coincide with said lines, when the angle is read upon the face of the protractor by the position of the pointer.

To hold the arms in any desired position.

to lay oit an angle, the post a is split longitudinally and the sleeve contracted about the pintle by means of a holding-screw h. As a result of the above arrangement, the arms are enabled to swing in the same plane. Thus in laying off angles upon any plane surface both arms rest thereupon, and more accurate work can be done than when the arms are hinged but swung in different planes, so that one would close over orbe superimposed above theother. y

The posts a b are of considerable lengthfm order to raise the protractor some distance above the plane in which the arms are located, in order to al'i'ord more Space for the artisan to center the instrument and enable him to see easily beneath the p1'otracter,wl1ile objectsy can bc placed between said arms to d e termine the angle of their surfaces.

That I claim is- 1. An instrnmentfor laying out or measur ing,` angles, composed of Jtwo arms graduated or otherwise and jointed togetherat one of the corners of each of Said arms to swing in the same plane abouttheir jointed connection, one of the said arms having rigidly connected therewith a protractor and the other of the Said arms having a rigidly-connected pointer arranged to swing` over the Said protractor,substantially as set forth.

2. In combination with a pair of arms graduated or otherwise and adapted to swing in one and the same plane about a central point located at the corner of one end of each of these arms, a pivot-al connection above or bclow said arms composed of: two vertical posts, one at the end of each arm,a Sleeve upon one post, and a pintle upon lhe opposite post, the central longitudinal axis of ihc pintle being coincident with and normal to the central swinging point of? the arms, Substantially as Stated.

The arm A, graduated or otherwise, its vertical post a at one end, the sleeveoset c, and a protractor surmonnting and ailixed to Said post, combined with the arm B, graduated or otherwise, to swing in the Same plane as arm A, its post l), the pintle (Z within the sleeve c,the pointer j', fastened upon the end of the pintle, and locking mechanism to hold the arms fixed, substantially as specified.

In testimony whereof I ailix my sig-n ature in presence of two witnesses.

(iITRISTOPHICH S. REAMY.

\Vitnesses:

ll. E. Leinen, E. K. BoYNroN. 

